1. Field of the Invention
The present invention relates generally to a method and apparatus for scheduling data considering power of the data in a communication system.
2. Description of the Related Art
Intensive research on the 4th Generation (4G) communication system, or the next generation communication system, is being conducted to provide to users services having various Quality of Service (QoS) classes at a data rate of about 100 Mbps. In particular, active research into the 4 G communication system is being conducted to support high-speed services by guaranteeing mobility and QoS for a Broadband Wireless Access (BWA) communication system such as a wireless Local Area Network (LAN) system and a wireless Metropolitan Area Network (MAN) system, and an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system is a typical BWA communication system.
The IEEE 802.16 communication system employs Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) to support broadband transmission networks for physical channel of the wireless MAN system. OFDM/OFDMA can transmit multiple subcarriers with orthogonality being kept therebetween, thereby obtaining the optimal transmission efficiency during fast data transmission. In addition, OFDM/OFDMA, as it is high in frequency efficiency and robust against multi-path fading, can obtain the optimal transmission efficiency during fast data transmission. Further, OFDM/OFDMA, as it uses frequency spectra in an overlapping manner, is high in frequency efficiency, is robust against frequency selective fading and multi-path fading, can reduce Inter-Symbol Interference (ISI) using a guard interval, and can be designed with an equalizer having a simple hardware structure. The communication system employing OFDM/OFDMA can include Wireless Broadband Internet (WiBro), or 2.3-GHz band Portable Internet Service.
The communication system employing OFDMA should appropriately distribute resources to increase channel utilization between multiple Mobile Stations (MSs), located in one cell, and a Base Station (BS). A subcarrier is one of the sharable resources in the communication system employing OFDMA, and the subcarriers are channelized. The optimal channel utilization is guaranteed depending on how the subcarriers are assigned to the MSs in the cell using a predetermined scheme. Herein, a set of at least one subcarrier will be referred to as a subchannel.
Data transmission of the BWA communication system is achieved on a frame-by-frame basis, and each frame is divided into an interval capable of transmitting downlink data and an interval capable of transmitting uplink data. The uplink/downlink data intervals each are divided again into the frequency axis and the time axis. Each element formed in a two-dimensional arrangement of the frequency axis and the time axis is called a ‘slot’.
Therefore, for assignment of downlink data bursts for MSs, the BS uses MAPs defined as normal MAPs or new normal MAPs (also known as Hybrid Automatic Repeat reQuest (H-ARQ) MAPs). The data bursts are assigned in the downlink data interval over multiple time slots. The BS performs power boosting or power deboosting on the assigned data bursts, thereby increasing the downlink resource utilization. In the BWA communication system standard, the power boosting/deboosting levels are defined as −12, −9, −6, −3, 0, 3, 6, 9, 12 dB.
However, a power assignment algorithm of performing the optimal power boosting/deboosting on the data bursts causes a very complex programming problem, so it can be hardly realized in the actual communication system.